1. Technical Field
The present invention relates in general to an improved hydraulic coupling, and in particular to an improved hydraulic coupling that compensates for trapped fluid volume when the coupling is attached or detached.
2. Description of the Prior Art
Hydraulic couplers that are mounted to subsea equipment are provided with sealed protective covers to protect their mating components from corrosion such as calcification. During subsea installations or operations, the protective covers trap a small but significant volume of sea water after the seals of the coupler engage, but before the poppets of the coupler are opened. To complete the installation, the trapped volume of fluid must be compressed to high pressure to force the poppets to open. The pressure required is approximately 400 psi greater than the pressure by the hydraulic couplers. The trapped volume of fluid is then introduced into the hydraulic circuit. If the hydraulic circuit is blocked in any manner, the additional volume of fluid can prevent installation of the protective cover. During removal of the protective cover, the same volume of fluid is still trapped. However, during removal of the cover a vacuum is developed prior to the seals of the coupler disengaging. The vacuum pressure far exceeds the installation differential pressure of 400 psi,, since the poppets do not open in both directions (e.g., the poppets only allow fluid flow in, not out).
In the prior art, this problem is typically overcome by welding an adapter to the back side of the hydraulic coupler and attaching one end of a short section of a flexible hose to the adapter. The opposite end of the hose is capped in hope that the hose acts as a pressure compensator. Unfortunately, the hoses installed must be rated for the hydraulic system operating pressures, and usually provide an insignificant amount of accumulation. This solution is particularly unworkable in high pressure applications on the order of 15,000 psi. Moreover, as the number of couplers that are mated at one time continues to increase, so does the installation and removal forces required to manipulate their protective covers. In addition, the cost of machining the adapter, welding it to the hydraulic coupler, and then installing the hose sections along with the required fittings is disproportionately high. Thus, an improved solution for compensating for pressure and the volume of trapped fluid in a hydraulic coupling during the attachment and detachment of the protective cover is needed.
A volume compensator has a body with an axial chamber containing a piston assembly that is biased to one side by a spring. The compensator is coaxially mounted with a female coupler to a protective cover for a hydraulic interface plate. The female coupler has an axial bore containing a poppet assembly with an axial bleed port that extends into a receptacle on the end of the female coupler. The receptacle receives a male coupler on the interface plate. The male coupler contains a poppet assembly with a solid poppet that seals in high pressure hydraulic fluid.
When the cover is secured to the interface plate, the male coupler is inserted into the receptacle and a small amount of sea water is trapped in between. The trapped sea water is forced through the bleed port and female coupler, and into the compensator where it displaces the piston and spring in the compensator. When the tips of poppets engage, high pressure hydraulic fluid is released into the female coupler and compensator where it is retained. When the cover is detached from the interface plate, the tips of the poppets disengage to seal off the high pressure hydraulic fluid. As the male coupler is withdrawn from the receptacle, the spring returns the piston to its starting position and ambient sea water is drawn into the chamber in the compensator.
The foregoing and other objects and advantages of the present invention will be apparent to those skilled in the art, in view of the following detailed description of the preferred embodiment of the present invention, taken in conjunction with the appended claims and the accompanying drawings.